Global analysis of nitrogen and phosphorus limitation

The cycles of the key nutrient elements nitrogen (N) and phosphorus (P) have been massively altered by anthropogenic activities. Thus, it is essential to understand how photosynthetic production across diverse ecosystems is, or is not, limited by N and P. Via a large-scale meta-analysis of experimental enrichments, we show that P limitation is equally strong across these major habitats and that N and P limitation are equivalent within both terrestrial and freshwater systems. Furthermore, simultaneous N and P enrichment produces strongly positive synergistic responses in all three environments. Thus, contrary to some prevailing paradigms, freshwater, marine and terrestrial ecosystems are surprisingly similar in terms of N and P limitation.

关键营养元素氮（Nitrogen, N）与磷（Phosphorus, P）的循环过程已因人类活动发生剧烈改变。因此，探明不同生态系统的光合生产是否受氮、磷限制，具有重要的科学意义。本研究通过对养分富集实验开展的大规模元分析（meta-analysis）发现：各类主要生境中磷限制效应的强度均处于相近水平；且陆地与淡水生态系统内，氮限制与磷限制的程度相当。此外，同时施加氮与磷富集的实验处理，在三类生境中均能引发极强的正向协同响应。综上，与部分主流学术范式相悖的是，淡水、海洋与陆地生态系统在氮、磷限制规律方面，表现出出人意料的高度相似性。